thermowell vs surface
- Thread starter Minbari
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I’ve done my own experiments. It depends on fermenter material, how vigorous the fermentation is and ambient temperature.
Plastic is the worst for being off by the most since heat transfer is not very good. The next is glass, it transfers heat better and the difference is less, stainless is better and the difference is less. At lager temperatures the difference is less on all three because exothermic activity is the least. At high ale temperatures the the difference between surface and thermal well is greater.
Your mileage may vary, but be aware that the material in fermentation vessel makes a huge difference.
Plastic is the worst for being off by the most since heat transfer is not very good. The next is glass, it transfers heat better and the difference is less, stainless is better and the difference is less. At lager temperatures the difference is less on all three because exothermic activity is the least. At high ale temperatures the the difference between surface and thermal well is greater.
Your mileage may vary, but be aware that the material in fermentation vessel makes a huge difference.
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I did forget to mention that this is stainless. the ambient temp is 65°
Also depends on your temperature control system's capacity. The thermowell is measuring the middle of the wort, and there can be a significant lag in the temperature if all you are doing is changing ambient. That leads to bigger temperature swings.
Surface mounting isn't measuring quite as accurately, because the Ambient has such a strong influence on the reading, but it does help moderate the temperature swings.
An immersion chiller works better with the thermowell.
If you are familiar with PID principles, a thermowell has the effect of increasing D, leading to oscillations around the setpoint
Surface mounting isn't measuring quite as accurately, because the Ambient has such a strong influence on the reading, but it does help moderate the temperature swings.
An immersion chiller works better with the thermowell.
If you are familiar with PID principles, a thermowell has the effect of increasing D, leading to oscillations around the setpoint
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Do you have insulation over the probe for the surface mount?
For surface mount temperature measurement in the process industries, a few things are required.
1. A good conductive surface. Stainless is good.
2. A reasonably-sized piece of insulating material over the probe to prevent error due to ambient temperature affecting the probe.
3. Ideally, turbulent flow in the pipe or vessel. You won’t have that in a fermenter. But during active fermentation, the beer does circulate and will come to a reasonably homogeneous temperature if the entire vessel is insulated.
For surface mount temperature measurement in the process industries, a few things are required.
1. A good conductive surface. Stainless is good.
2. A reasonably-sized piece of insulating material over the probe to prevent error due to ambient temperature affecting the probe.
3. Ideally, turbulent flow in the pipe or vessel. You won’t have that in a fermenter. But during active fermentation, the beer does circulate and will come to a reasonably homogeneous temperature if the entire vessel is insulated.
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DING! Bubba you're a mind reader. When I did this experiment, it was with glass and my external probe was covered with a patch of fiberglass insulation just so the "ambient" and the surface would be isolated.... within reason. Lemme go find that thread...
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Here we go....
Brewersfriend.com/forum/threads/temperture-deltas.12046/#post-89452I
Looks like I was doing this in the warmer weather and in the chamber so any heating element I was using was would have bumped up the ambient temperature in the chamber so just theoretically in a cold environment with a highly thermal conductive fermentation vessel, delta's abound!
So, like snowflakes, our processes differ but when we try out the scientific method we need to replicate our conditions as best identical as able or like HVM said...
Brewersfriend.com/forum/threads/temperture-deltas.12046/#post-89452I
Looks like I was doing this in the warmer weather and in the chamber so any heating element I was using was would have bumped up the ambient temperature in the chamber so just theoretically in a cold environment with a highly thermal conductive fermentation vessel, delta's abound!
So, like snowflakes, our processes differ but when we try out the scientific method we need to replicate our conditions as best identical as able or like HVM said...
Cool experiment. I'm glad I've got my probe in the wort these days so probably reading more accurately.
My big takeaway has been regardless of probe placement providing yeast with stable temps to do their Thing.
My big takeaway has been regardless of probe placement providing yeast with stable temps to do their Thing.
My fermenter is located in the garage. In the spring and fall, we can get quite significant temperature swings, so I have both heating and cooling hooked up. I have a stainless Brewtech fermenter with a neoprene jacket. For cooling, I use chilled water through the lid mounted heat exchanger coils. For the heating, I use a seedling mat that wraps about halfway around the vessel. To control the cooling, the temperature probe goes into the thermowell. For the heating control, I have a separate controller with the probe placed directly on the surface of the fermenter under the neoprene jacket, roughly at 180 degrees around from the center of the seedling mat.
During active fermentation, the temperatures for the heating and cooling probes are within about 1 degree. This is likely due to movement (very slow movement) of the wort in the fermenter caused by release of CO2. After the very active fermentation is complete, I'll see a 2-3 degree difference sometimes, particularly if it is very warm or very cold in the garage.
A thermowell will generally work better than a surface mount. However, a surface mount probe can be used with pretty decent accuracy if you make a small modification and place some insulation over the probe. For a plastic fermenter located in a chamber where you're controlling air temperature, I would tape a 6" x 6" piece of neoprene or double thick Reflectix. This should work well if you don't have a thermowell. And in a temperature controlled fridge, you won't get the extremes of ambient temperature.
During active fermentation, the temperatures for the heating and cooling probes are within about 1 degree. This is likely due to movement (very slow movement) of the wort in the fermenter caused by release of CO2. After the very active fermentation is complete, I'll see a 2-3 degree difference sometimes, particularly if it is very warm or very cold in the garage.
A thermowell will generally work better than a surface mount. However, a surface mount probe can be used with pretty decent accuracy if you make a small modification and place some insulation over the probe. For a plastic fermenter located in a chamber where you're controlling air temperature, I would tape a 6" x 6" piece of neoprene or double thick Reflectix. This should work well if you don't have a thermowell. And in a temperature controlled fridge, you won't get the extremes of ambient temperature.
I use bubble wrap insulation from Home Depo on the kettle, mash tun and all fermenters. Would make a good insulation for surface Mount. I use thermowells now but still insulate everything.
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A couple years ago I borrowed a coworkers Tilt to compare actual wort temperature to side of fermenter temperature. The probe on the side of the glass carboy fermenter was covered by 1/2 inch styrofoam. The temperature difference between the two was similar to what @Bubba Wade noted; except I saw a 2-3°F difference during active fermentation and only a 1°F difference after a week or so. After I reluctantly gave the Tilt back I would factor in that offset when setting my Inkbird controller.
I didn't mention my Tilt as it's not used for control. But it always reads about 2 degrees higher than the others. Most likely due to convection.
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Mine does that once the active fermentation is done.
